Endless belt for electrophotographic apparatus

Abstract

An endless belt for use as an intermediate transfer belt or a transfer-sheet transfer belt in an electrophotographic apparatus using electrophotographic technologies such as a full-color LBP (Laser Beam Printer) or a full-color PPC (Plane Paper Copier). At least a base layer of the belt comprises a modified polyamide imide resin formed by copolymerizing: (A) an aromatic isocyanate compound; (B) an aromatic polycarboxylic acid anhydride; and (C) a polymer having carboxylic acids at both terminals thereof.

1. An endless belt for transferring a toner image to be used in an electrophotographic apparatus, the belt being circumferentially driven in a state that a surface of the belt is in contact with or is adjacent to a photoreceptor of the electrophotographic apparatus, wherein a base layer of the belt comprises a modified polyamide imide resin formed by copolymerizing: (A) an aromatic isocyanate compound; (B) an aromatic polycarboxylic acid anhydride; and (C) a polymer having carboxylic acids at both terminals thereof, wherein a content of a structural unit induced from the polymer having carboxylic acids at both terminals thereof (component (C)) is within a range from 5 to 30% by weight based on a total amount of the modified polyamide imide resin. 
     
     
       2. The endless belt according to  claim 1 , wherein the component (C) is at least one polymer selected from the group consisting of polybutadiene having carboxylic acids at both terminals thereof, hydrogenated polybutadiene having carboxylic acids at both terminals thereof, polyester having carboxylic acids at both terminals thereof and polyamide having carboxylic acids at both terminals thereof. 
     
     
       3. The endless belt according to  claim 1 , wherein the base layer is formed by the modified polyamide imide resin and phosphorus-containing polyester resin. 
     
     
       4. The endless belt according to  claim 1 , wherein the anhydride of the component (B) is a combination of an aromatic polycarboxylic acid anhydride (B1) and an aromatic polycarboxylic acid dianhydride (B2). 
     
     
       5. The endless belt according to  claim 4 , wherein molar ratio of the component (B1) and the component (B2) is (B1)/(B2)=90/10 to 50/50. 
     
     
       6. The endless belt according to  claim 1 , wherein the component (A) is a combination of diphenylmethane diisocyanate (MDI) and tolidine diisocyanate (TODI). 
     
     
       7. The endless belt according to  claim 1 , wherein the modified polyamide imide resin formed by copolymerizing the components (A) to (C) has an elongation at break within a range of 20 to 55%. 
     
     
       8. The endless belt according to  claim 1 , wherein the modified polyamide imide resin formed by copolymerizing the components (A) to (C) has an elongation modulus within a range of 2300 to 4700 MPa. 
     
     
       9. The endless belt according to  claim 1 , wherein the endless belt has a creep rate within a range of 0.1 to 0.3%, the creep rate being obtained by: cutting the belt into a strip so as to prepare a testpiece having a size of 20 mm×180 mm; hanging up the testpiece with a load of 250±5 g applied to an end thereof allowing the testpiece to stand at 50° C.×95% for 24 hours; and calculating the creep rate of the testpiece. 
     
     
       10. The endless belt according to  claim 1 , wherein a surface layer is formed on an outer peripheral surface of the base layer. 
     
     
       11. The endless belt according to  claim 10 , wherein the surface layer is formed of a silicone-grafted acrylic resin which is a graft polymer having an acrylic resin (main chain) grafted with a silicone resin.